Constant speed body



June 29, 1943.

G. LUCKEY CONSTANT SPEED BODY Filed Nov. '24, 1937 3 Sheets-Sheet 1 FIG.

650. P. Lycxzr FIG.8

IIIIIIII'IIIIIIIIIII VIII'III'IIIIIIIII INVENTGR.

ATTORNEYS June 29, 1943. P, LU Y 2,322,861

CONSTANT SPEED BODY 2 Filed Nov. 24, 1937 3 Sheets-Sheet 2 E 45 4| 4s as1 as f 1 I h 1 a 5 77/ W 3 7 I 54 35 I as '7 12 lzlr 23 I J J as I'6'50. 1? Lac/ Er 2 m II 2: [IT Q uvwzzvmk I Y g7 nc x FIG. 3 RESPOMSWEATTORNEYS. owner 4 June 19434 G. P. LucKEY CONSTANT SPEED BODY FiledNov. 24, 1937 3 Sheets-Sheet 3 650. P. LUC/(EY INVENmR. BYWZ;%

Ammvsys.

Patented June 29, 1943 I 2,322,861 CONSTANT SPEED BODY Y George P.Lackey, Lancaster, Hamilton Watch Company,

Pa., assignor to Lancaster, Pa.

Application November 24,1937, Serial No. 176,297

27 Claims.

The object of this invention is to obtain an exactly constant speedrotating body. This is preferably done by mounting upon an approximatelyconstant speed body, a second body which is periodically controlled toexactly constant speed.

A further object of thisinvention is to provide mechanical means andinstrumentalities by which approximately constant rotation can becontrolled by exactly constant impulses to effect exactly constantrotation.

A further object of this invention is to provide improved means fortesting a moving body under observation by means of an exactly constantspeed rotating shaft. A still further object is to provide improvedmeans for supporting and operating a testing device.

Further and more specific objects, features, and advantages will moreclearly appear from a consideration of the specification hereinaftertaken in connection with the accompanying drawings which form part ofthe specification, and which illustrate several forms the invention maytake.

In the drawings:

Fig. 1 is a diagrammatic view illustrating the apparatus embodying myinvention, and as used for watch timing.

Fig. 2 is a diagram showing the cumulative effect of error.

Fig. 3 is an enlarged sectional view of the rotat ing system illustratedin Fig. 1.

Fig. 4 is a, plan view of the correcting portionof the rotating system'.

Fig. 5 is a modification of Fig. 4 showing a different type rotor orcorrection arm. I

Fig.6 is a top view of the particular type motor taken on the line 6-6of Fig. 3.

Fig. 7 is a modified form of rotating system.

Fig. 8 is another modification of the upper end of the rotating system.

Fig. 9 is a further modification of the upper end of the rotatingsystem.

Fig. 10 is still a further modification of the upper end of the rotatingsystem.

Although it is expensive and diificult to obtain a rotating body whichwill-rotate at an exactly constant speed, it is fairly cheap andinexpensive to obtain an oscillating body whose period is exactlyconstant. For many purposes it is desirable to have a constant speedrotating body, as such a body has many advantages over an oscillatingbody. An oscillating body can only be used for timing objectswhere theperiod of the period of the oscillating body. On the other hand, a bodyrotating with an exactly uniform velocity can be used by stroboscopic orother means to obtain accurate timing of devices which timing may be anysmall fraction of the rotational period of the said body. In thefollowing invention a method is described whereby the accuracy easilyobtainable with an oscillating system can be transformed to obtain abody rotating at exactly constant speed.

It is relatively easy to obtain a body rotat-' ing at approximatespeeds. This can be done with an electric motor either by the induction,series, or synchronous type or by a spring motor with a centrifugalgovernor. Such a motor can be made to carry on its rotating elementanother rotating body free to rotate thereon but bound to the rotatingbody with a light frictional contact. Such frictional means can eitherbe the pivot bearings carrying th second rotor, a lightly pressedfrictional spring, or frictional means such as air or liquids If themotor is thenset in rotation, the second rotor will eventually assumethe velocity of the first rotor for by so doing the frictional dragbetween the two moving objects will then be a minimum The second rotorbeing lightly coupled to the first rotor will, over a period of time,assume the average speed of the first rotor. Changes in speed in thefirst rotor will require considerable time to efiect the second rotor,due to the light frictional coupling, so that the second rotor will belittle influenced by any rapid accelerations or decelerations of thefirst rotor.

It is desirable, however, in inany cases to obtain a more constantrotational velocity of the second rotor than can be obtained by itsassuming the average rotational speed of the first rotor. To this enduse is made of impulses of whatever kind, obtained from an exactlyconstant period oscillating body. Such a constant period oscillatingbody may be a pendulum of a clock, a tuning fork, element of achronograph, fine watch, or other time piece, or any other exactlyconstant period body. An impulse canibe picked up at one portion of thepath of the oscillating body either by an electrical contact in the pathof the oscilof various types.

the periodic oscillating time pieces 2 ruption of the light beam whichis picked up by a photo-electric cell and amplified to give a uniformrecurring impulse, or by many other arrangements. This impulse can thenbe transferred to the first rotating body through brushes and by meansof electro-magnets properly placed, was jets, or other mechanical meanswhich ght affect the rotation of the second rotor.

One general way of accomplishing this is as follows: assume that thereare stationary electromagnets through which a periodic electricalimpulse is sent from a clock. On the second rotating bodyis an arm whichmay be in the shape of a bar, a rectangular-like shape, or a compositeelement having more than two poles or projections. The speed of thefirst rotating body is so adjusted that it is approximately in step withthe periodic impulses. When these impulses occur, the arm on the secondbody, and rigidly fastened to it, may be either ahead or behind theposition of the energized magnets. The electrical impulses will thencause the magnets to receive a deceleration if the arm is ahead of, andan acceleration if the arm is behind, the central position in which itlines up with the magnets. In this way each time the magnet receives anelectrical impulse the arm receives a correction or a check on its speedso that it is held in step with the period of the oscillating body atone or more points in its path. It has been found that, at times, theaction of the arm would tend to be unsteady to a very small degree. Polefaces were attached to the electro-magnets, but that did not solve theproblem. After much research and experimentation the damping cup orfriction cup was invented, which always'gives smooth and steadyoperation. The cup or ring is mounted .on the first rotating body, andmovement of the cup creates either air or liquid currents which resultina frictional pull against the second, rotating body causing the secondbody to follow the first body although always, of course, lagging behindin time in accelerating and decelerating.

By adjusting the strength of the impulses, the frictional couplingbetween the first and second rotors, and the approximate speed of thefirst rotor, it is possible to obtain a rotating arm whose rotationalperiod will be veryclose to if not equal to that of the controllingelectrical impulses; and because of the inertia of the second rotatingbody, its rotational velocity between, the moments at which it isaffected by the electrical impulses will be very constant.

The above general principles of means to obtain an exactly constantperiod of rotation will be now specifically applied to testing a watchand the devices invented therefor. However, it is to be understood thatthis method and apparatus is not limited to its use to this particularfield,

nor limited to the very accurate timing of any oscillating,reciprocating, or vibrating unit, but is claimed in its broadest aspectas described hereinbefore in the general description of the invention.

In the'checking of watches or other esca'pement itis customary to allowthese to operate over a long period of time, for example twenty-fourhours, to determine whether are correctly timed. In case the timing canbe checked to one second in twenty-four hours an error of plus or minusone second in 86,400 seconds is possible, which means that the error ofa watch can, by timing it over a twenty-four hour period, be checkedwithin one part in 86,400. To

they.

I obtain accurate timing by this method it is necessary that the watchbe placed under for long periods of time, and it is not possible toobservation wheel, when illuminated byv flashes of light occurring withextreme accuracy at constant intervals. In the following description themethod is described in its application and in connecton with the timingof a conventional watch escapement, consisting of a balance wheel andhairspring forming the oscillating system which are driven by a palletand fork from an escape wheel.

A radius of the balance wheel, as for example the balance arm inoscillating moves from the position in which it would be at rest in caseit were not oscillating (hereinafter called the zero position) to aposition where the hairspring is stressed to its maximum. When thisposition is reached the balance wheel comes to a stop, and reversing itsmotion starts to move in the oppoe site direction. Up to the time thebalance wheel reaches zero position the energy stored in the hairspringis supplied to the balance wheel, in-

creasing its speed, until at the zero position there is no longer anytension in the hairspring and the balance wheel has attained its maximumspeed. From this point on, the balance wheel stores its kinetic energyas potential energy in the hairspring, and the hairspring is stressed inthe opposite direction. The balance wheel continues its motion until allits energy of motion has been transferred into a stress in thehairspring; at which point the balance wheel stops, and again starts tomove in the reverse direction:

As long as sufllcient'energy is supplied to overcome energy lost throughfriction, the balance wheel will oscillate back and forth, and ifproperly designed the oscillations of the balance wheel will be veryconstant. The time for a complete oscillation of the balance wheel, thatis, the time required to move from zero position to the point where thehairspring has received its maximum stress in one direction then throughzero position to the point where the hairspring has received its maximumstress in the opposite direction and again back to its zero position isthe period of oscillation of the balance wheel.

In watches the period of the balance wheel is usually two-fifths second.In case a watch has a two-fifths second period and is accurately timedthe balance wheel will pass zero position every one-fifth second, and asit passes through this zero position it will have its maximum velocity.Thus, every one-fifth second the balance arm of the watch will be seenpassing its zero position, first going in one direction and then in theoposite direction, and will'be traveling with its maximum velocity.. I

Now, if a light were made to illuminate the balance wheel for a veryshort period of time, say one-three thousandth second, each time thebalance arm is in its zero position the balance arm will be illuminatedfor such a short time that it will "appear to remain stationary. Thisstationary image of the balance arm will be seen in one case when thebalance arm is passing in one direction, the next time when the balancearm is passing in the opposite direction. From this it can been seen ifthe flashes of light are occurring exactly one-fifth second apart and ifthe position in the v make the balance'arm appear asaaser flashinglight.

wheel is a trifle shorter than two-fifth second,

and to start with the light is made to flash at the time the balance armis in its zero position, the next time the light flashes the balance armwill have passed through its zero position and gone a trifle beyond. Onits next return the balance arm will go twice as far beyond the zeroopposite direction, on the next passage three times as far, etc. Thus,for each succeeding flash of light the balance arm will be seen fartherfrom its zero position, the images alternating right and left. If such abalance wheel is observed by means of a flashing light and thetime ofthe light'flash is adjusted to stationary at its zero position, first asingle image of the balance arm will be observed. Then as time passesthe images of the balance arm moving in opposite directions will nolonger be at the zero position and the observed effect will be a slightflicker in the image of th balance arm. This flicker will increase asthe images of th balance arm move farther and farther from their zeroposition until flnally two distinct images of the balance arm areobserved on either side of the zero position. These two images duringfurther observation will appear to move farther apart. From this it canbe seen that if the period of the balance wheel is not the same as theperiod of the flashing light,

this fact can be quickly noticed.

This method of observing the difference in rates between the balancewheel and the flashing light is extremely sensitive. Assume, forexample, that the balance wheel has an amplitude of turn, that is, thatthe balance arm moves turn to the right and turn to the left from thezero position. The velocity of 'the balance at its zero position will besuch that it would make a turn, if th velocity would remain constant, inapproximately /24 second. Assuming that by the above method a differenceof /100 of one turn between the two images of a balance arm would benoticeable by the flicker produced, then this /100 of a turn differencewould be produced when one image was /200 of a turn to the image /200 ofa turn to the left of the zero position. The time necessary for.

right and the other move /200 of a turn past the be about View of asecond. From this it can be seen that as soon as the difference in timebetween the balance wheel ,and the flashing light amounts to /4800second, a noticeable flicker of the balance arm will be observable. Inother words, if the two images of the balance arm traveling in oppositedirections are superimposed, then a change in the rate of the balancewheel with respect to the flashing of the light of /4800 of a secondwill be observable. If, after the superposition of the balance armimages, a minute is required for the flicker to become observable thenthe balance wheel is gainthe balance arm to zero position would ing atthe rate of /4800 second a minute or seconds in twenty-four hours. Thus,in on minute greater accuracy can be obtained by this method of timingthan can be obtained in twenty-four hours by the conventional method.

The same effect in the changing of the position of the balance arm imagewould be observable if the watch were running slower than the Thi ismade more apparent in Fig. 2, which shows a balance wheel and arm andalso a chart showing the different positions of the balance arm atdifferent times. Point A on this chart shows the position of the balancearm each time it is illuminated by a flashing light if the flashinglight has half the period of the balance. Point 13 shows the position ofthe balance arm image in successive stages if the period of the balancearm is shorterthan the flashing light, and the points designated C showthe position of the balance arm if the balance is greater than theperiod of the flashing light. I Y

To obtain the illumination of the balance arm it is desirable to have aflashing light in which the time at which the light flashes can bereadily changed to make the light flash sooner or later without changingthe time between the light flashes. In this way the light can be'made toilluminate the balance arm in any position and can be adjusted'so thatthe balance arm is illuminated when at its zero position. Then, if thehalf period of the balance arm and the period of the light are not thesame, the time at which the light flashes can at a later time beslightly changed until the balance arm is again in its zero position. Ifthe balance arm is faster than the flashing light the light can be madeto flash at an earlier time, and if it is slower than the flashinglight, the light can be made to flash later. Then the amount it has beennecessary to change the time of the light flashes I ance arm to its zeroposition after a certain elapsed time will give an exact measurement ofthe time change between the two and the period of the balance wheel.Whether it is necessary to speed up or slow down the time at which thelight flash occurs will show whether the watch is running fast or slow.a

A mirror, 49, is mounted upon a shaft 46, rotating at exactly 300 R. P.M., thus making a revolution every one-fifth second. A light source, II,and lens, H, are placed above the rotating shaft directed toward themirror so that the light is reflected and the image of the light, as themirror thrown around a circle centered in In case a slit, II, is placedon the circumference of this circle and the light is allowed to shinethrough it into the watch, the light will be thrown through this slitonce during each revolution of the rotating shaft. If the slit is ,6inch wide and the circumference of the circle on which the image of thelight source is cast is 60 inches, then the light will traverse thecircumference every one-fifth second for a period of 0 second. If thebalance wheel is placed behind this slit it will be illuminated duringthis period of time. Now, if the housing or mounting "5, for rotatingshaft, 46, is rotated, or if the slit is moved around the rotatingshaft, the light can be made to flash at a time ing upon the amount themounting or the slit is moved. Howevenas soon as this movement hasstopped, the time between the flashes will be exactly one-fifth secondapart. In case the mounting, l6, of the rotating shaft or the slit, I5,is moved one complete turn, the time at which the light flashed willsecond. If the housing or slit is moved /60 turn. the flashes occur willhave sooner or later dependand the phase of half period of the to againbring the bal have been changed one-fifth the flashing light is adjustedby moving the rotor mounting or the slit until the balance arm appearsin i s zero position without flicker, then if after observing thebalance arm I for one minute it is found that the rotor mounting has tobe moved in the direction of'rotation it turn to bring the images of thebalance arm together again, this will show that in onggninute the watchhas gained 5 of a second or it is gaining at the rate of less than $5second, i. e., second, a day. A reverse rotation of the rotor mountingof the same amount to superimpose the images would show a loss in therate of the" watch of the-same amount.

There are two ways to obtain correctly timed light flashes, or whatamounts to the same thing,

a, shaft which will rotate at exactly a constant speed. One of theseways is to drive a motor at approximately constant speed, and to mounton the rotor shaft of the motor a second rotor or correction arm whichis in very light frictional engagement therewith. This correction arm isthus free to turn on the rotor shaft of the motor when it is attractedat accurately timed periodic intervals by another force, and the arm cantherefore be rotated at exactly constant speed. This apparatus is shownin Figs. 1-6, and 8-10.

asoaaoi The other method is to drive a motor by an alterhating currentwhich has an extremely constant frequency such as can be obtained from aquartz crystal oscillator or a vibrating tuning fork, controlled by amaster clock, or by any other means which may furnish extremely constantfrequency. This apparatus is illustrated in Figs. 1, 2, and 'l.

The mounting or housing It containing the motor assembly and the upperrotor or correction arm assembly, is securely fastened to shaft 29 whichin turn is journaled in base 21. To the neck of the base auxiliary dialis is fastened, while to the movable shaft 29 auxiliary pointer 20 andworm gear 18 are fastened.

The bearing and stationary pointer 22 are movably supported with respectto the base 2'! by stud 24. Shaftlb having a worm H at one end, and anadjusting knob and main dial at the other end is rotatably supported inbearing 25. If the worm i1 is out of engagement with the worm gear it!the housing It may be quickly movedto get'a magnets M3, is operative.

and the other end of which is fastened to the slip ring directly above.The two lowermost brushes connect the two bottom rings to the source ofapproximately constant current such as is commercially available andwhich is indicated at A. By fastening the line wires A to the support 28instead of connecting the wires directly to the coil or rings 33prevents the wires from becoming entangled and torn during the moving ofmounting It. When the coil it slip ring,

is-energized it induces a field of one polarity in one set of polepieces, and a difierent polarity in the other set of pole pieces therebycausing the rotor 38 of the motor to operate at approximately constantspeed.

Rotor 3b is fastened on a shaft 39 which rotat'es on insulation 51positioned on the upper end. of shaft 25. Said shaft 39 has asemi-circular knob it on the upper end, and a circular damping cup Mintermediate. its ends. The shaft 39 passes through a guide 52 havingupwardly extending arms 43 which support electromagnets M having polefaces 52 thereon. The upper rotor or correction arm 65 rests upon thesemi-circular head 40, and although thearm is in light frictionalengagement therewith it is free to rotate faster or slower when anotherforce, such as supplied by the energised electro- The arm as may be ofany width, and may be very narrow as shown in Fig. 5 at 65. The arm ispreferably of soft iron or other highly permeable metal, but may beformed instead of a permanent magnet. In

- the latter case, however, a complete revolution quick adjustment ofthe phase of the light flashes to bring the balance arm to its zeroposition. The worm ll may then be engaged and a fine adjustment securedfor observing changes in the time 01 the watch which is being tested.The stationary pointer 22 then indicates on the movable main dial 2 I,and the movable pointer 20 indicates on the stationary auxiliary dialIS, .the degree of. rotation of the mounting required by the error ofthe balance wheel, and data necessary to correct the error. The reasonfor the two dials is for the purpose of reading the instrument eitherfrom a standing or sitting position, and providing also an accuracycheck on any reading.

The insulated rod 28 is fastened to base 21 and, extending through theslot 3| in the mounting 16, carries the brushes 32 which slide on theslip rings 33. These slip rings are carried by insulated rods which aresupported either on the plate 34 or the bottom of the mounting l5. Theslot 3| may be of any length short of 360 must be made betweenenergizing periods instead of a half revolution as in the case of a softiron bar. If desired, the number of electromagnets maybe increased forgreater sensitivity. A shaft 65, made in one or two pieces, extendsupwardly through the guide ti and has a mirror or other deflectingsurface 63 adjustably mounted thereon by means of thumb screw 48. Inmoving the mounting it, the rotor 38 follows the pole pieces, and thearm 65, by means of the light frictional engagement with the head 40,also tends to follow the mounting. When current is supplied to the coil,the rotor almost instantly attains approximately constant speed.

For a short while the speed of the arm lags far behind the speed of therotor because of the slippage between the head and the arm, butgradually the arm rotates at the same speed as the rotor. By supplyingexactly constant periodic excitation such as might be controlled by aslave pendulum, a master clock, or by some other means, through theleads B to the electromagnets M, the speed of the arm can be advanced orretarded slightly, and thus the arm and deflecting surface kept rotatingat exactly constant speed. The damping or friction cup 41, sometimesalso called a stabilizing cup or ring as previously mentioned tends toaccelerate or decelerate the speed of the arm to its own speed by reasonof its movement setting up air currents and air friction which operateonthe arm thus providing extremely smooth operation.

In Figures '7 and 10, as well as in Figure 3, the deflecting surface isshown mounted on a shaft extending from a rotating element, while inRiga. 8 and 9, the reflecting surface 69' is mounted on the rotatingelement. The configuration of the rotating element might be such as toprovide a reflecting surface itself.

Fig. 8 shows a modified point support forthe asaaacr to keep said arm incorrection arm. Rotor l8 and damping cup 4| are secured to shaft 39-11.A narrow strip 58 extends inwardly from the cup to provide a support forthe pin 53. By adjusting the screw 53 the friction between the rotorshaft 13-12 and the arm shaft 46' may be either increased or decreased.

Figs. 9 and 10 illustrate damping rings 4|", fastened to the rotorshafts 39' and 3!" respectivelyand filled with water, oil, or some otherliquid. In addition to the light frictional engagement between themoving element, the liquid also provides friction for stabilizingpurposes- In the device illustrated in Fig. 9 the force of theelectro-magnets is lessened slightly by being positioned at a distancefrom the arm, while in Fig. 10, which shows the correction arm andelectro-magnets elevated above the liquid damping bath, the full forceof the correctly timed impulses is exerted directly on the am. In Figs.9 and 10 the cup 54 and hollow receptacle 54' respectively provide acertain amount of buoyancy to counteract the weight of the arm.

Fig. 7 illustrates a testing device which may be used where exactlyconstant frequency current is available. In this modification only twoslip rings and two brushes are necessary. 0,

indicates leads to a source of exact constant frequency power.

The testing devices are illustrated with reflecting surfaces which turnat the same speed as the arm. However, the arm might as easily be usedto operate any sort of indicating device or scale, in which anapproximate constant speed of rotation is checked or corrected, ifnecessary,

to an exact constant speed of rotation.

What I claim is:

1. An apparatus for producing an exactly constant speed rotating shaftcomprising a constant frequency source of electrical energy, a mounting,a shaft, a rotor fixed to said shaft, a stator electromagneticallyconnected to said rotor'and fixedly positioned within said mounting,slide rings within the mounting connecting said stator to said constantfrequency source of electrical energy, said slide rings permittingappreciable travel of the mounting so that the constant speed shaft willtake more or less time to make a complete revolution if the mounting isbeing moved and indicating means mounted on said shaft.

2. An apparatus comprising an element rotatable at approximatelyconstant speed, a second element in light frictional engagement with thefirst element and driven thereby, electromagnetic means for controllingthe second element to exactly constant speed by timed impulses at shortintervals by periodically accelerating or decelerating the speed of thesecond element.

3. An apparatus comprising an element driven at approximately constantspeed, a second element carried by said first element, said secondelement being in light frictional engagement with the first element,electro-magnetic means energized at periodic intervals to bring saidsecond element to exactly constant speed, and an indicating devicesupported y and rotated byv the second element.

4. An apparatus for producing an exactly constant speed rotating bodycomprising a motor, a shaft, a rotor on said shaft which revolves atapproximately constant speed, an arm in light frictional engagement withtheshaft, and means causing rotation or for exactly constant speed byelectromagnetic lmlmlses.

5. An apparatus comprising a stator, a rotor, and a stabilizing. dampingcup, a shaft for fixedly supporting both said rotor and saidstabilizing, dam-ping cup, means to rotate said shaft, a correction armfrictionally supported by and movable on'said shaft. said stabilizingcup surrounding said correction arm so as to produce a damping effectupon said correction arm thereby tending to prevent rapid accelerationand deceleration, an indicator supported by said arm, and means forsupplying a periodic force to said correction am so that said correctionarm will rotate at a constant speed.

6. An apparatus comprising a mounting, a synchronous motor, a correctionarm within the mounting, a shaft for said motor rotatable atapproximately constant speed, said correction arm frictionallypositioned on said motor shaft, magnetic means energized at periodicconstant intervals to attract said arm, a shaft extending from said arm,and a reference member mounted on said shaft.

'7. An apparatus comprising a motorhaving a shaft rotatable atapproximately constant speed, a second shaft impositively connected tosaid motor shaft, an arm mounted on said second shaft, electromagneticmeans energized from an exactly constant source of supply andelectromagnetically connected to said second shaft to control saidsecond shaft, and reference means mounted on said am, and rotating withsaid arm.

8. .An apparatus for producing exactly constant speed rotationcomprising a motor,'a shaft on said motor, a second shaft mounted on andnormally turning with said first mentioned shaft,

a correction arm and a deflecting surfacemounted on said second shaft,and electro-magnetic means energized from an exactly constant source ofenergy so as to cause said correction arm and deflecting surface to turnat a rate, different than the rate of, the first mentioned shaft.

9. An apparatus for producing constant rotation comprising a synchronousmotor, a shaft for said motor, a head forming the upper end of theshaft, a correction arm supported on said head and free to turn withrespect thereto, indicating means mounted on said arm, means energizedat periodic constant intervals to correct said am by electromagneticimpulses, and slide rings for said motor so that the apparatus may beturned through any angle.

10. An apparatus for measuring time intervals comprising a source ofelectrical energy, a motor comprising a stator and an approximatelyconstant speed rotor, a body supported by and motivated impositively bysaid rotor, said body having an indicating surface, electromagneticmeans to act on and cause said body to rotate at exactly constant speed,and slide rings connecting said stator with said source of electricalenergy whereby said stator may be rotated throughout any angle withoutbeing disconnected from the source of energy.

11. An apparatus of the character described comprising a referencemember, means to drive the reference member at substantially constantspeed, a tick responsive device adapted to respond to ticks of a masterwatch, and actuating means controlled by the tick responsive deviceoperatively connected to additionally control the movement of thereference member to synchro- 'nize the reference member with the master-watch.

12. An apparatus of the character described comprising a rotatablereference member, a shaft arranged to impositively drive said member.means to drive said shaft at a substantially constant speed, an armaturerotatable with said member, an .electromagnet positioned to cooperatewith said armature, a tick responsive device adapted to respond to ticksof a master watch, and an electrical circuit arranged to be closed bysaid tick responsive device and to energize said electromagnet.

13. An apparatus of the character described comprising a referencemember, means to drive the reference member at substantially constantspeed, a tick responsive device adapted to respond to ticks of a masterwatch, and actuating means controlled by the tick responsive deviceoperative to give an adjusting movement to the reference member tosynchronize the same with the master watch.

14. An apparatus of the character described comprising a rotatablereference member, means for rotating the reference member at asubstantially constant speed, a tick responsive device adapted torespond to ticks of a master watch, and adjusting means controlled bythe tick responsive device operative to retard the rotation of thereference member when the rtot'ation of the reference member leads withrespect to the master watch.

15. An apparatus of the character described comprising a rotatablereference member, means for rotating the reference member at asubstantially constant speed, a tick responsive device adapted torespond to ticks of a master watch. actuating means controlled by thetick responsive device operatively connected to give additional rotationto the reference member of an amount proportional to the extent to whichthe reference member lags relative to the watch, because of lack ofperfect synchronism.

16. An apparatus of the character described comprising a rotatablereference member, means to drive the reference member at a substantiallyconstant speed, a tick responsive device adapted to respond to ticks ofa master watch, actuating means, and magnetic means controlled by saidtick responsive device to rotate the reference member with respect tothe substantially constant speed driving means to compensate for lack ofsynchronism between said constant speed driving mechanism and the masterwatch. 7

1'7. An apparatus of the character described comprising a ,shaft adaptedto be rotated. at a substantially constant speed, a reference memberrotatably mounted on said shaft,'a tick responsive device adapted torespond to the ticks of a master watch, means controlled in response tosaid tick responsive device for rotating the reference member on theshaft to compensate for lack of synchronism between the referencememiber and the master watch. 3

18 In an apparatus for timing a moving body, a synchronous motorcomprising a rotor and a stator, a second rotor movably mounted on saidfirst rotor and driven thereby, and indicating means mounted on saidsecond rotor, said rotor being controlled to the proper speed at shortintervals by electromagnetic impulses from a constant frequency sourceof current.

19. In an apparatus for comparing the differ- I ence between standardfrequency impulses and unknown frequency impulses, a synchronous 1. 9-

aaeaaei tor, a rotor mounted on said motor in light frictionalengagement therewith and frictionally driven by the rotating part of themotor, but

being free to move independently of the rotating part of the motor, saidrotor being controlled to the proper speed by said standard frequencyimpulses, and indicating means including an element rigidly attached tothe rotor, and means for angularly adjusting, as a unit, the m'o/tor androtor a certain distance. r

20. Apparatus for determining the period of a body movable about acenter of motion and which forms a member of the control system of atime piece, which comprises means for producin accurately timed lightflashes at constant frequency, including a synchronous motor operated[by approximately constant frequency, a correcting rotor driven by saidmotor through a light frictional clutch, means to control said rotor tooperate at constant frequency, a rotatable support for said motorshiftable to change the phase of the light flashes.

21. In a watch testing apparatus, a stroboscopic device including alightsource and a rotatable member for comparing the rate of a watch'to betested with the rate of a master watch, means for impositively rotatingsaid member at substan-' tially constant speed, an armature rotatablewith said member, an electromagnet positioned to cooperate with saidarmature, and means for periodically energizing said electromagnet insynchronism with the beats of said master watch.

22. In a watch testing apparatus, a rotatable member, a shaft arrangedto impositively chive said member, means to rotate said shaft at asubstantially constant speed, an armature rotatable with said member, anelectromagnet periodically energized at a standard frequency to correctthe speed of said memberthrough the medium of said armature, and meansincluding said member and a light source co-operating with a part of thewatch beingtested to indicate the rate of said watch.

23. In a timing mechanism, a motor, a rotor, a slippable friction clutchinterconnecting the rotor and motor whereby to rotate the rotor normallyin synchronism with the motor, means for intermittently modifying thespeed of rotation of the rotor comprising an armature member affixed-tothe rotor, an electro-magnet and timed means adapted to intermittentlyenergize the magnet whereby to attract the armature and cause slippagein the clutch.

24. In a timing mechanism, a motor, a rotor, a slippable friction clutchinterconnecting the rotor and motor whereby to rotate the rotor normallyin synchronism with the motor, means for intermittently modifying thespeed of rotation of the rotor comprising an armature member aifixed tothe rotor, an electro-magnet and timed means adapted to intermittentlyenergize the magnet whereby to attract the armature and cause slippagein the clutch, said timed means comprising a time piece, means toenergize the magnet by the tick of said timepiece, the armature memberhaving a plurality of armature points adapted, during rotation of therotor, to pass successively through the area of the field of saidmagnet.

25. In a timing mechanism, a friction member rotated by a motor, amoving element having a frictional engagement with said member whereofrotation of the points of the armature and means for successivelyenergizing the magnet at equal periods to attract one of the points tothe core and thereby cause slippage in said frictional engagement,whereby to rotate the moving element by the motor but to intermittentlysynchronize the speed of rotation of the moving element with theintermittent energizing of the magnet.

26. An apparatus of the character described comprising a rotatablereference member. means for rotating the reference member at asubstantially constant speed, a tick responsive device adapted torespond to ticks of a master watch,

and actuating means controlled by the tick re the reference member.

27. An apparatus of the character described comprising a rotatablereference member, a shaft driven at a substantially constant speed onwhich said reference member is yieldably mounted, an armature rotatablewith said reference member, an electro magnet positioned to cooperatewith said armature, a tick responsive device adapted to respond to ticksof a master watch, and an electrical circuit arranged to be closed bysaid tick responsive device and to energize said electro magnet.

GEORGE P. LUCKEY.

